1. Field of the Invention
The present invention relates to a spacer structure for a linear guideway, the spacer is a unitary structure consisted of a plurality of parting portions, connecting portions and a retaining portion, and is suitable for mass production and can prevent the rollers from skewing and impacting from each other, thus ensuring a smooth operation of the linear guideway.
2. Description of the Prior Arts
With the development of science and technology, and the improvement of the precision feeding system, linear guideway and technology thereof have become a most important part of many precision mechanisms. Various types of linear mechanisms have been and are being widely used in different fields. Although the linear guideway technology is developing fast, still there are some problems of the linear products that need to be improved. Many efforts have been made by the related industry to effectively improve the quality of linear guideway, in particularly, those high precision mechanisms (such as wafer processing equipment and CNC Computer Numeric Control instruments) that need to run stably and silently. Therefore, there are still some blind spots in the existing linear mechanisms that need to be exploited and erased.
The existing linear guideways can generally be divided into three categories:
A. The first type linear guideway as shown in FIG. 1 generally includes a plurality of rollers 10 that are connected by a chain 12. The production of the chain 12 is considered as a core of the mould and comprises the following steps: first, putting the rollers 10 into the male and female moulds, and then ejecting plastic into the moulds. This type of linear guideway (JP Pat. No. 3,436,708 or U.S. Pat. No. 6,626,572) has the following disadvantages:                1. The number of rollers 10 is in proportion to the length of the chain 12, if the chain 12 is long, the number of rollers 10 should be relatively large, and the production time is relatively long.        2. Assembling the chain 12 with the rollers 10 is laborsome.        3. The chain 12 uses a plurality of spacers 11 to separate the rollers 10, the spacers 11 each has two concave contact surfaces for contacting with rollers 10 and the diameter of the concave contact surfaces of the spacers 11 is equal to that of the rollers 10. Therefore, the spacers 11 are in full surface contact with the rollers 10, this will lead to a great friction. And a long time of relative slide between the rollers and the spacer will increase the elastic fatigue of the chain.        
B. A second type linear guideway (disclosed by U.S. Pat. No. 3,964,802) as shown in FIG. 2 employs a plurality of spacers 13 to separate the rollers 10, each of the spacers 13 includes two retaining portions 131 to be inserted in the rollers 10, and a pair of strip portions 14 arranged between two neighboring rollers 10 for prevention of metal-slide-induced friction therebetween. The respective spacers 13 are alternatively arranged at either end of the respective pairs of rollers 10, that is to say, each of the rollers 10 is provided with a spacer 13. The disadvantages of this type linear guideway as explained as follows:                1. The rollers 10 should be formed at either end thereof with a hole for insertion of the retaining portions 131 of the spacers 13, this will not increase the processing cost but also weaken the strength of the rollers 10.        2. As compared with to the spacer with concave contact surface, the spacer 13 of the second type linear guideway occupies much more spaces of the linear guideway, such that the number of rollers 10 in a given length of linear guideway will be reduced, thus adversely affecting the load capacity and the rigidity of the linear guideway.        3. The spacers 13 in a line guideway cannot be made at one time but need to be assembled separately, therefore, the assembly is really time consuming.        
C. A third type linear guideway (disclosed by U.S. Pat. No. 6,390,678 and JP patent No. 11-351254) as shown in FIG. 3 comprises a conical connecting portion 15 connected between the respective rollers 10 and located along the radial direction of the rollers 10. Each of the rollers 10 is equally divided into halves, and the disadvantages of this type linear guideway as explained as follows:                1. since the connecting portion 15 is located along the radial direction of the rollers 10, and the radial direction of the roller is the most import loading direction of the linear guideway, it will substantially reduce the contact surface between the rollers and the slide groove of the slide block, and will largely weaken the load capacity and the rigidity of the linear guideway.        2. In the circulating channel, the conical connecting portion 15 will cause inference to the circulating channel because of weight, thus causing slide friction and affecting the smooth operation of the linear guideway.        The present invention has arisen to mitigate and/or obviate the afore-described disadvantages.        